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Author: Shipra Sethi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Seismic noise is the continuous oscillation of the Earth recorded at every station in the absence of earthquakes . The interaction of atmosphere, ocean waves and earth creates them. The dominant signal, called secondary microseisms in the frequency band 0.1-0.3 Hz have known to be formed due to the non-linear interaction between two oppositely traveling ocean gravity waves. The resulting pressure fluctuations close to the ocean surface generates a seismic signal which is dominantly Rayleigh waves (R). Many authors reported the observations of Love wave content (L) in the seismic signal. However the L/R amplitude ratio is shown to vary depending on the area investigated. The generation mechanism of Rayleigh waves due to these noise sources interacting with the sea-bottom is well understood and modeled. The explanation why Love waves are generated is unclear because the source in the ocean cannot generate shear motion. We have shown the existence of Rayleigh and Love waves recorded by the Alaska and California network. We then investigate the effect of ocean-continental slope boundary on the seismic noise amplitude of secondary microsiesm and quantify the Rayleigh-to-Love wave conversion. In order to do that, we use the spectral element method to numerically simulate the seismic wave field in 3D media. The primary focus of this study is on investigating several factors that can influence the seismic noise amplitude recorded on the continent in the frequency band 0.1-1 Hz. Those factors are a) the ocean-thickness, b) the source-site effect i.e., source close to the boundary and far from the boundary, c) the sedimentary layer beneath the sea-bottom and d) the effect of ocean-continental slope angle. We observe that Love waves can be generated at the ocean-continental boundary, however the amplitude change is frequency dependent. We observe energy in the transverse direction in a model that cannot generate Love waves as a result of conversion at the ocean-continental slope boundary. The strongest Love wave amplitude is recorded in a model with 6 km deep ocean at resonant frequencies in the ocean when the source is far from the coast. However at other frequencies, shallow oceans and source close to the boundary generates highest Love wave amplitude. In the presence of sediments, the amplification of Love waves is higher at shorter periods for both sources. The reduction in slope angle diminishes the Love wave amplitude. For both source close and far from the boundary, the L/R amplitude ratio vary strongly with frequency and ocean thickness. Among all the factors, highest L/R amplitude ratios are generated due to sediments when the source is close to the boundary.
Author: Shipra Sethi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Seismic noise is the continuous oscillation of the Earth recorded at every station in the absence of earthquakes . The interaction of atmosphere, ocean waves and earth creates them. The dominant signal, called secondary microseisms in the frequency band 0.1-0.3 Hz have known to be formed due to the non-linear interaction between two oppositely traveling ocean gravity waves. The resulting pressure fluctuations close to the ocean surface generates a seismic signal which is dominantly Rayleigh waves (R). Many authors reported the observations of Love wave content (L) in the seismic signal. However the L/R amplitude ratio is shown to vary depending on the area investigated. The generation mechanism of Rayleigh waves due to these noise sources interacting with the sea-bottom is well understood and modeled. The explanation why Love waves are generated is unclear because the source in the ocean cannot generate shear motion. We have shown the existence of Rayleigh and Love waves recorded by the Alaska and California network. We then investigate the effect of ocean-continental slope boundary on the seismic noise amplitude of secondary microsiesm and quantify the Rayleigh-to-Love wave conversion. In order to do that, we use the spectral element method to numerically simulate the seismic wave field in 3D media. The primary focus of this study is on investigating several factors that can influence the seismic noise amplitude recorded on the continent in the frequency band 0.1-1 Hz. Those factors are a) the ocean-thickness, b) the source-site effect i.e., source close to the boundary and far from the boundary, c) the sedimentary layer beneath the sea-bottom and d) the effect of ocean-continental slope angle. We observe that Love waves can be generated at the ocean-continental boundary, however the amplitude change is frequency dependent. We observe energy in the transverse direction in a model that cannot generate Love waves as a result of conversion at the ocean-continental slope boundary. The strongest Love wave amplitude is recorded in a model with 6 km deep ocean at resonant frequencies in the ocean when the source is far from the coast. However at other frequencies, shallow oceans and source close to the boundary generates highest Love wave amplitude. In the presence of sediments, the amplification of Love waves is higher at shorter periods for both sources. The reduction in slope angle diminishes the Love wave amplitude. For both source close and far from the boundary, the L/R amplitude ratio vary strongly with frequency and ocean thickness. Among all the factors, highest L/R amplitude ratios are generated due to sediments when the source is close to the boundary.
Author: Z. S. Andrianova
Publisher: Springer Science & Business Media
ISBN: 1468486047
Category : Science
Languages : en
Pages : 99
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Book Description
Among seismic waves generated by widely dilferent types of sources, the waves that are the most interest ing and of the longest duration are usually surface waves (which are also called normal waves, interference and channel waves, natural vibrations of layers, etc. ). These waves are distinguished by their dispersion and reso nance, and are used in many investigations - in the determination of the structure of the medium (the existence of surface layers and waveguides), in the determination of the coordinates and properties of the source (in par ticular its energy and mechanism), in the identification of subterranean exploSions, in the mapping of micro-ยท seisms, in the tracing of storms, etc. Outlines of the wide literature concerning surface waves can be found in [2, 9, 40J. Surface waves can be classed as Rayleigh or Love waves, depending on their velocity and polarization: the displacements of particles in Rayleigh waves are parallel, and the displacements in Love waves perpendicular, to the vertical plane containing the direction of propagation (some variation from this polarization is possible close to the source or in the presence of horizontal inhomogeneities in the medium). The present work is devoted to the calculation and investigation of Love waves in a vertically layered medium. The method used is based on the spectral theory of linear differential operators. ' This method is much more effective than previously applied methods based on the approximation of the medium by a set of homogeneous layers.
Author: Nori Nakata
Publisher: Cambridge University Press
ISBN: 1108417086
Category : Nature
Languages : en
Pages : 373
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Book Description
A comprehensive overview of seismic ambient noise, covering observations, physical origins, modelling, processing methods and applications in imaging and monitoring.
Author:
Publisher: Academic Press
ISBN: 0123809398
Category : Science
Languages : en
Pages : 180
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Book Description
The critically acclaimed serialized review journal for over 50 years, Advances in Geophysics is a highly respected publication in the field of geophysics. Since 1952, each volume has been eagerly awaited, frequently consulted, and praised by researchers and reviewers alike. Now in its 52nd volume, it contains much material still relevant today--truly an essential publication for researchers in all fields of geophysics. - Contributions from leading authorities - Informs and updates on all the latest developments in the field
Author: Haruo Sato
Publisher: Academic Press
ISBN: 012380938X
Category : Mathematics
Languages : en
Pages : 181
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Book Description
The critically acclaimed serialized review journal for over 50 years, Advances in Geophysics is a highly respected publication in the field of geophysics. Since 1952, each volume has been eagerly awaited, frequently consulted, and praised by researchers and reviewers alike. Now in its 52nd volume, it contains much material still relevant today--truly an essential publication for researchers in all fields of geophysics. Contributions from leading authorities Informs and updates on all the latest developments in the field
Author: Brian Kennett
Publisher: ANU E Press
ISBN: 192153673X
Category : Reference
Languages : en
Pages : 298
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Book Description
Seismic Wave Propagation in Stratified Media presents a systematic treatment of the interaction of seismic waves with Earth structure. The theoretical development is physically based and is closely tied to the nature of the seismograms observed across a wide range of distance scales - from a few kilometres as in shallow reflection work for geophysical prospecting, to many thousands of kilometres for major earthquakes. A unified framework is presented for all classes of seismic phenomena, for both body waves and surface waves. Since its first publication in 1983 this book has been an important resource for understanding the way in which seismic waves can be understood in terms of reflection and transmission properties of Earth models, and how complete theoretical seismograms can be calculated. The methods allow the development of specific approximations that allow concentration on different seismic arrivals and hence provide a direct tie to seismic observations.
Author:
Publisher: Elsevier
ISBN: 0444538038
Category : Science
Languages : en
Pages : 5604
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Book Description
Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole
Author: Caineng Zou
Publisher: Elsevier
ISBN: 0128122358
Category : Technology & Engineering
Languages : en
Pages : 508
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Book Description
Unconventional Petroleum Geology, Second Edition presents the latest research results of global conventional and unconventional petroleum exploration and production. The first part covers the basics of unconventional petroleum geology, its introduction, concept of unconventional petroleum geology, unconventional oil and gas reservoirs, and the origin and distribution of unconventional oil and gas. The second part is focused on unconventional petroleum development technologies, including a series of technologies on resource assessment, lab analysis, geophysical interpretation, and drilling and completion. The third and final section features case studies of unconventional hydrocarbon resources, including tight oil and gas, shale oil and gas, coal bed methane, heavy oil, gas hydrates, and oil and gas in volcanic and metamorphic rocks. - Provides an up-to-date, systematic, and comprehensive overview of all unconventional hydrocarbons - Reorganizes and updates more than half of the first edition content, including four new chapters - Includes a glossary on unconventional petroleum types, including tight-sandstone oil and gas, coal-bed gas, shale gas, oil and gas in fissure-cave-type carbonate rocks, in volcanic reservoirs, and in metamorphic rocks, heavy crude oil and natural bitumen, and gas hydrates - Presents new theories, new methods, new technologies, and new management methods, helping to meet the demands of technology development and production requirements in unconventional plays
Author: Roman Teisseyre
Publisher: Springer Science & Business Media
ISBN: 3540313370
Category : Science
Languages : en
Pages : 582
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Book Description
This breakthrough book is the first to examine the rotational effects in earthquakes, a revolutionary concept in seismology. Existing models do no yet explain the significant rotational and twisting motions that occur during an earthquake and cause the failure of structures. The rotation and twist effects are investigated and described, and their consequences for designing tall buildings and other important structures are presented. This book will change the way the world views earthquakes.
Author: F. A. Dahlen
Publisher: Princeton University Press
ISBN: 0691216150
Category : Science
Languages : en
Pages : 1040
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Book Description
After every major earthquake, the Earth rings like a bell for several days. These free oscillations of the Earth and the related propagating body and surface waves are routinely detected at broad-band seismographic stations around the world. In this book, F. A. Dahlen and Jeroen Tromp present an advanced theoretical treatment of global seismology, describing the normal-mode, body-wave, and surface-wave methods employed in the determination of the Earth's three-dimensional internal structure and the source mechanisms of earthquakes. The authors provide a survey of both the history of global seismological research and the major theoretical and observational advances made in the past decade. The book is divided into three parts. In the first, "Foundations," Dahlen and Tromp give an extensive introduction to continuum mechanics and discuss the representation of seismic sources and the free oscillations of a completely general Earth model. The resulting theory should provide the basis for future scientific discussions of the elastic-gravitational deformation of the Earth. The second part, "The Spherical Earth," is devoted to the free oscillations of a spherically symmetric Earth. In the third part, "The Aspherical Earth," the authors discuss methods of dealing with the Earth's three-dimensional heterogeneity. The book is concerned primarily with the forward problem of global seismology--detailing how synthetic seismograms and spectra may be calculated and interpreted. As a long-needed unification of theories in global seismology, the book will be important to graduate students and to professional seismologists, geodynamicists, and geomagnetists, as well as to astronomers who study the free oscillations of the Sun and other stars.
